tony it sounds as though the jag main stealers ( oops mean't to say dealers ) are trying to weedle out of replacing your damaged engine. you could have lost oil from the engine due to bad workman ship by the technician who changed your oil at the last service ( forgot to tighten the sump plug , oil filter or even used the wrong oil ).
before the engine exploded did any of the warning lights come on low oil pressure or low oil level ext.?.
i think personally that you should speak to jaguar themselves and any of the main stealers.